Search

We report room-temperature terahertz sources based on Cˇerenkov difference-frequency generation in dual-wavelength mid-infrared quantum cascade lasers with giant resonant optical nonlinearities originating from intersubband transitions. A Cˇerenkov difference-frequency generation scheme allows for extraction of THz radiation along the whole length of the laser waveguide and provides directional terahertz emission. Experimentally, our sources demonstrate a conversion efficiency of up to 70 μW/W2 approximately an order of magnitude improvement over the previous reports. [ABSTRACT FROM AUTHOR]

Semiconductor heterostructures are the basic materials underlying optoelectronic devices, particularly lasers and light-emitting diodes (LEDs). Made from various III-V-, II-VI-, SiGe- and other compound semiconductors, modern semiconductor devices are available for the generation, detection and modulation of light covering the entire ultra-violet to far-infrared spectral region. Recent approaches that introduced multilayer heterostructures tailored on the lower nanometre scale made possible artificial semiconductors with new properties, such as extended wavelength coverage, that enabled new applications. Together with ongoing progress on wide-gap semiconductors, the optical wavelengths accessible by semiconductor devices are steadily expanding towards the short-wavelength ultra-violet regime, as well as further into the far-infrared and terahertz spectral regions. It is the aim of this focus issue to present cutting-edge research topics on the most recent optoelectronic material and device developments in this field using advanced semiconductor heterostructures. [ABSTRACT FROM AUTHOR]

Abstract: A miniaturized optical carbon-monoxide sensor based on tunable diode laser spectroscopy is presented and tested for various applications. It utilizes recently developed Vertical-Cavity Surface-Emitting Lasers (VCSELs) emitting at 2.3 μm as light source and the photodetector housing as integrated gas reference cell. Together with a wide/narrow spectral scan algorithm for wavelength stabilization, a compact, self-monitored and microcontroller-based sensor is realized. In contrast to conventional line-locking, the full wavelength scale of the spectral scans is inherently calibrated. The achieved sensing resolution (1 sigma) is 3 ppm for 1 second averaging. [Copyright &y& Elsevier]

We report the design and performance of terahertz quantum cascade laser sources based on intracavity difference frequency generation in dual-wavelength mid-infrared quantum cascade lasers with a passive nonlinear section at the exit facet, designed for giant second-order nonlinear susceptibility. These devices operate in the mid-infrared at λ1=8.4 μm and λ2=9.5 μm, with terahertz output at the difference frequency, λ3≈73 μm. Terahertz output of approximately 100 nW was observed up to a heat sink temperature of 210 K. [ABSTRACT FROM AUTHOR]